The central nervous system (CNS), and the brain in particular, perform some of the most complex and essential processes in the human body. Surprisingly, contemporary health care often lacks the tools to objectively and effectively assess brain function at the point-of-care. A person's mental and neurological status is typically assessed using an interview and a subjective physical exam. Clinical laboratories may not have the capacity to effectively assess brain function or pathology, and may be largely limited to the identification of poisons, toxins, drugs, or other foreign substances that may have impacted the central nervous system (CNS).
Brain imaging technologies, such as computed tomography imaging (CT), magnetic resonance imaging (MRI), positron emission tomography (PET), and single photon emission computerized tomography (SPECT) may be used to visualize the structure of the brain. Yet these anatomical tests may reveal little information about brain function. For example, intoxication, concussion, active seizure, metabolic encephalopathy, infections, diabetic coma, and numerous other conditions may show no abnormality on a CT scan. Even a stroke or a traumatic brain injury (TBI) may not be immediately visible in an imaging test, even when a person has dearly observable abnormal brain function. CT and MRI may only detect a change in brain function after the morphology or structure of the brain has changed. Thus, in some cases, it may take hours or days after the onset of a condition before severe neurological pathology is visible on the CT or MRI.
Such limitations may be especially significant after trauma, because the brain may require immediate attention to avoid further deterioration. For example, diffuse axonal injury (DAI), related to shearing of nerve fibers and present in many concussive brain injury cases, may remain invisible on most routine structural images. If undetected at an early stage, swelling or edema from DAI may lead to coma and death.
Functional MRI (fMRI), a recent improvement over MRI, provides relative images of the concentration of oxygenated hemoglobin in various parts of the brain. While the concentration of oxygenated hemoglobin may be a useful indication of the metabolic function of specific brain regions, it may provide limited or no information about the underlying brain function, i.e., the processing of information by the brain, which is electrochemical in nature. Another recent improvement, diffusion MRI (dMRI) maps the diffusion process of molecules, such as water, in the brain and may provide details about tissue architecture. One type of dMRI, diffusion tensor imaging (DTI), has been used successfully to indicate abnormalities in white matter fiber structure and to provide models of brain connectivity. DTI may provide a viable imaging tool for the detection of DAI, but such imaging again focuses on anatomical information rather than brain function.
All of the brain's activity, whether sensory, cognitive, emotional, autonomic, or motor function, is electrical in nature. Through a series of electrochemical reactions, mediated by molecules called neurotransmitters, electrical potentials (voltages) are generated and transmitted throughout the brain, traveling continuously between and among a myriad of neurons. This activity establishes the basic electrical signature of the electroencephalogram (EEG) and creates identifiable frequencies that may have a basis in anatomic structure and function. Understanding these basic rhythms and their significance may make it possible to characterize the electrical brain signals as being within or beyond normal limits. At this basic level, the electrical signals may serve as a signature for both normal and abnormal brain function. Just as an abnormal electrocardiogram (ECG) pattern is a strong indication of a particular heart pathology, an abnormal brain wave pattern may be a strong indication of a particular brain pathology. Additionally, the electrical activity of the brain may be affected closer to the onset of a condition, before any structural changes have occurred.
Even though EEG-based neurometric technology is generally accepted today in neurodiagnostics, its application in the clinical environment is notably limited. Using standard EEG technology, it may take a skilled technician 1 to 4 hours to administer a test. A neurologist must then interpret the data and make a clinical assessment.
Furthermore, some equipment used for recording EEG data may be too bulky or may be inappropriate for certain situations. For example, standard EEG equipment may require a technician to individually apply 19 or more electrodes onto the scalp of a subject. Each electrode must be placed directly onto the scalp of the subject (often with a conductive gel or paste) in the correct location on the subject's head. Applying the electrodes, each with its own lead wire, may be tedious and time consuming, taking thirty minutes or longer to complete. Application may be further complicated because the electrode wires may easily become tangled and may interfere with other operations. The lack of portability of EEG technology may make it infeasible for point-of-care applications.
To make EEG technology easier to apply to a subject, some products have incorporated electrodes into nets or caps that may be placed on the subject's head. Once in position, a technician can then individually place and attach each electrode to the scalp. While this may decrease preparation time, it still requires a technician to place each electrode.
Other products have tried to eliminate the need to individually place each electrode by allowing an administrator to apply all of the electrodes at once to a subject. Such products fix the relative positioning of electrodes in a headset, which may then be fitted to the subject. Thus, by incorporating all of the electrodes into a headset and fixing their relative location, placement of the electrodes is complete once the headset is positioned on the subject, substantially reducing the preparation time. Such technology has worked to some extent for anesthesiologists in sedation applications, for example, to detect whether a person's EEG readings indicate proper sedation based on pre-sedation and post-sedation readings of that same person. Yet, grouping the electrodes in this manner has proven surprisingly inadequate and unreliable for capturing EEG readings capable of discriminating between levels of normal versus abnormal brain activity for a given person relative to a population.
Without a quick and reliable way of placing electrodes for EEG readings, current EEG equipment and electrode arrays may not be practical for the emergency room (ER), operating room (OR), intensive care unit (ICU), first response situations, sporting events, the battlefield, or other point-of-care settings and situations. Thus, there is an immediate need for a portable brain state assessment technology to provide rapid neurological evaluation and treatment guidance for subjects with acute brain injury or disease, so as to prevent further brain damage and disability. This in turn may help medical personnel select an immediate course of action, prioritize people for imaging, and determine whether immediate referral to a neurologist or neurosurgeon is required.
Embodiments of the disclosure described herein may overcome some disadvantages of the prior art.